The present invention relates to a display device and control method thereof. More particularly, the present invention relates to a bi-stable display, a frame updating method and a timing control method.
The bi-stable display technic is a common name of a display technic. Hitherto, cholesterol display technic and electronic ink display technic are the most known. In the bi-stable display technic, for example, the electrophoresis display, an on/off action of the display can be implemented by a motion of the charge particle, and its timing controller is connected to a microprocessor of the system which can drive the electrophoresis display through a drive chip after receiving command order and image data. Furthermore, the bi-stable can still have two different states (bright state and dark state) without voltage and maintain continuously. Therefore, the image can be held on the display without voltage and reduce power consumption effectively. Widely speaking, bi-stable display technic is growing with more and more displaying gray scale/color depth, i.e. multi-stable display technic. In contrast with the prior art pure liquid crystal display technic, the bi-stable technic with the frame memory function does not need the backlight so that it can save several hundred times of the power consumption and become thinker and lighter. This characteristic can extend life of a battery of a portable device, for example, mobile phone, electronic book, electronic newspaper and electronic tag, and even large electronic bulletin board.
In drive of the bi-stable display, for example, the electrophoresis display, the drive method is similar with the pulse width modulation (PWM). The corresponding impulse provided to the electrophoresis display by the source driver is controlled by a timing controller. The normal source drive voltage levels are positive voltage (VPOS), negative voltage (VNEG) and 0 volt (GND) respectively. The positive and negative voltage is depend on material of the electrophoresis display, and some material need to be provided higher voltage for changing the gray scale of images in unit time effectively. Please refer to FIG. 1, it is a schematic diagram of the conventional source drive output voltage of the bi-stable display during image updating period. As shown in FIG. 1, the image updating period has frames F1˜F8. The positive and negative high voltage levels V1 and V2 (not shown) of the adjacent frames F1 and F2 are (+15) and (−15) volt respectively, and there is a voltage level with 0 volt. As shown in FIG. 1, the source drive output voltages of the adjacent frames F3 and F4 are switched directly at high voltage level V2 and V1, and the source drive output voltages of F1 and F2 are switched directly to V1 from V2. In updating frame, the drive method of the gray scale of each pixel is determined by the last frame, the next frame, and the environment temperature. Therefore, the present drive method are usually switched directly at high voltage level which belongs high voltage difference and fast voltage transfer. Therefore, other signals have enormous noise coupling so that the frame appears image unstable, un-uniformity, ghosting, crosstalk and over power consumption easily.